A RECENT study has explored the effects of very-low-calorie ketogenic diets (VLCKD) and Mediterranean diets (MD) on gut microbiota and metabolic health. Conducted by researchers from Brazil and Italy, the year-long study followed newly diagnosed Type 2 diabetes (T2DM) and obesity (diabesity) patients, aiming to assess how these diets influence metabolic outcomes and microbial diversity.
T2DM, often linked to visceral obesity, arises from impaired insulin secretion and activity, leading to elevated blood sugar and systemic inflammation. The gut microbiota plays a pivotal role in metabolic processes, influencing immune response, inflammation, and insulin sensitivity. Altered gut microbiome composition has been linked to metabolic disorders, prompting interest in dietary interventions to restore microbial balance.
While the Mediterranean diet is recognised for its cardiometabolic benefits, the long-term effects of VLCKD on gut health and metabolism remain under-researched.
The study followed 11 participants, aged 45 to 65, with newly diagnosed T2DM and no prior treatment. Attrition reduced the cohort to eight by the 12-month mark. Patients were randomly assigned to either VLCKD or MD protocols. VLCKD participants initially consumed protein-based meal replacements with minimal carbohydrates (<30g/day) for two months, transitioning to the Mediterranean diet by the fourth month. The MD group focused on plant-based foods, moderate protein intake, and balanced macronutrients throughout.
Clinical and microbiome assessments occurred at baseline, six months, and 12 months. Researchers measured body mass index (BMI), waist circumference, blood glucose, and cholesterol levels, alongside analysing gut microbiota through 16S rRNA sequencing.
Both diets improved metabolic health, but VLCKD demonstrated greater mid-term benefits. By six months, the VLCKD group showed significant BMI (-5.8 kg/m², p=0.006) and HbA1c (-1.2%, p=0.02) reductions. Beneficial gut bacteria, such as Akkermansia, increased during the ketogenic phase but declined after transitioning to MD.
However, VLCKD raised concerns about long-term sustainability, with reductions in muscle mass and increased LDL cholesterol levels noted.
The study highlights the potential of VLCKD for short-term metabolic and microbial improvements in diabesity patients. It also emphasises the need for personalised dietary strategies and long-term investigations to optimise health outcomes while mitigating risks.
Reference
Palmas V et al. Impact of Ketogenic and Mediterranean Diets on Gut Microbiota Profile and Clinical Outcomes in Drug-Naïve Patients with Diabesity: A 12-Month Pilot Study. Metabolites. 2025;15(1):22.
